Security systems have been devised in the past in which a number of sensors such as ultrasonic, microwave, switch contact, fire security, etc., are coupled by a multi-wire cable to a central control unit. The central control unit in many instances has local annunciation in terms of a sounder which provides an audible indication of an alarm condition signal having been transmitted to the central control unit. Additionally, the central control unit may have an annunciation of the location of the sensor producing the alarm condition indicating signal. Moreover, many of these security systems are provided with means for testing the system in which, for instance, an off-premises telephone dialer is inhibited so that the system may be tested without transmission to a fire station, a police station or off-premises security office.
While various previous security systems have sensors at which are located lights which are made to flash when the particular sensor has been violated, such as by passing in front of an ultrasonic sensor, it is not clear from a walk test of such sensors that the output of the sensor is, in fact, being communicated to the central control unit utilized for such a sensor. Nor is it clear that the central control unit is operative to process the alarm condition signal. Compromise of the system between the sensor and the control unit includes, for instance, cable tampering, either intentional or accidental, and a walk test while giving a degree of certainty as to the operability of the sensor itself, does not provide an indication of the communication of the sensor's output to a central unit and beyond.
Perhaps a more important problem with the testing of security systems is the lack of constant reminder that the system is in the test mode. While systems in the past have provided test indicator lamps at a central control panel, when personnel are engaged in testing of the system at points remote from the panel, there is no indication that the system is in a test mode in which alarms are inhibited and in which communication to the outside world has been temporarily cut. Thus, for instance, should a fire occur while the system is in a test mode, personnel not aware of the system being in a test mode might assume that the fire alarm indicating signal had, in fact, been sent off-premises.
The problem is compounded when, as is the usual case, the burglar alarm/fire alarm control unit is completely disabled and a separate test unit is connected to the system in order to test the entire system. While the test unit itself may be located adjacent the control unit, there is no necessity for co-locating the units and if the system test lamps are only located at the test unit control panel, the fact of the system being in the test mode will not be communicated to other personnel, either at the central control unit or elsewhere in the protected facility.
It is, of course, possible that the individual initiating the test sequence will forget that the system has been placed in a test mode and will leave the premises. In such a case the premises are left with no protection at all, since the major system functions have been inhibited to enable the test.